The problem of separating oily or hydrocarbon substances (hereinafter simply referred to as "oils") dispersed into aqueous solutions, namely of the total separation of the insoluble oily phase from the aqueous phase containing the dispersed fraction of the oily phase, has been examined by various experts, and different techniques have been proposed and used up to date.
In the separation process, the difficulty notably increases when wishing to reduce to a minimum the residual amount of oils in water, after separation. This difficulty determines also an increase in the operating costs.
The known techniques adopted so far include, for example, absorption on active substances (e.g. active carbon), distillation, decantation through packed blades, ultrafiltration and centrifugation.
All the aforecited techniques show some inconveniences which greatly limit their feasibility, especially when operating on large quantities of water which must be "cleaned" from oil residues to the greatest possible extent: gravimetric separations, for instance, are limited by the availability of sufficient differences of density between the aqueous phase and the oily phase, especially when treating very fine emulsions: thermic separations involve considerable energy costs and are unproposable for application on a vast scale, as in oil separation from surface waters; the techniques making use of membranes have the drawback of low productivity and suffer from fouling problem.
It is of common knowledge, now-a-days, that huge volumes of oil-polluted surface waters have to be treated so as to restore the proper environmental conditions, since the presence of oils is harmful for the environment, the water life and the general use of the water resources. There is hence at present an unsatisfied demand for an innovating technology, apt to be economically applied--in removing oils from water--on a vast scale.